Domain authentication over vpn

I'm setting up a satellite office that will have a site-to-site VPN to a main office with a domain controller. This office will hold a application server and a handful of workstations and will have it's own subnet and network services provided by the firewall. It will need to access the DC for authentication as well as limited shares on that main location network.

I've not ever set up an environment like this, so I'm looking for best practices. I'll assume that even if I have a VPN that sees both subnets, I'll need a rule that directs specific traffic to the IP of the DC at the main location. If this is the case, is there a set of services that need to be routed by a firewall rule? If so, Please suggest the services/ports/and protocols - or even a link to a "how-to".

My original thought was that I could delineate auth traffic only and point that to the main office and everything else would be handled locally, but I don't know that's even possible or recommended. Any suggestions would be greatly appreciated as I would like to make this as efficient as possible.

I'm using a Sonicwall TZ215 firewall as well as a Cisco SG200 series layer-3 switch.

Who is Participating?

1. Keep authentication local, install a local DC and ensure DHCP is installed on the DC
2. Ensure to create a Site in AD Sites and Services and add the subnet IP to this site
3. Ensure your DC is configured as a GC (AD Sites and Services)

For whatever reason if you cannot install a local DC and DHCP then I would recommend to create a new scope on one of your DHCP and then configure IP Helper address.

I'd have a second DC at the remote office if possible that way you not only have built-in redundancy for your DC but replication traffic is far less significant than the traversing everything over the VPN.